Force invariant touch sensitive actuator

ABSTRACT

A user interface for a lighting control has a touch sensitive front surface; a four-wire resistive touch pad responsive to a point actuation on the front surface, the touch pad having a longitudinal resistive element for providing a first control signal representative of the position of the point actuation along the longitudinal axis, and a lateral resistive element for providing a second control signal representative of the position of the point actuation along the lateral axis; a controller receiving the first and second control signals; a first capacitor coupled between the lateral resistive element and a circuit common that charges and discharges through the longitudinal resistive element of the resistive touch pad to stabilize the first control signal; and first, second, and third switches controlled by the controller to provide a DC supply voltage to the resistive elements and to couple a respective resistive element to the controller. The controller determines, from the second control signal, if the touch sensitive front surface is presently being actuated, and determines, from the first control signal, the position of the point actuation along the longitudinal axis.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 11/471,914, filed Jun. 20, 2006 entitled FORCE INVARIANT TOUCH SENSITIVE ACTUATOR.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to load control devices for controlling the amount of power delivered to an electrical load from a power source. More specifically, the present invention relates to a touch dimmer having a touch sensitive device.

2. Description of the Related Art

A conventional two-wire dimmer has two terminals: a “hot” terminal for connection to an alternating-current (AC) power supply and a “dimmed hot” terminal for connection to a lighting load. Standard dimmers use one or more semiconductor switches, such as triacs or field effect transistors (FETs), to control the current delivered to the lighting load and thus to control the intensity of the light. The semiconductor switches are typically coupled between the hot and dimmed hot terminals of the dimmer.

A conventional two-wire dimmer has two terminals: a “hot” terminal for connection to an alternating-current (AC) power supply and a “dimmed hot” terminal for connection to a lighting load. Standard dimmers use one or more semiconductor switches, such as triacs or field effect transistors (FETs), to control the current delivered to the lighting load and thus to control the intensity of the light. The semiconductor switches are typically coupled between the hot and dimmed hot terminals of the dimmer.

Smart wall-mounted dimmers include a user interface typically having a plurality of buttons for receiving inputs from a user and a plurality of status indicators for providing feedback to the user. These smart dimmers typically include a microcontroller or other processing device for providing an advanced set of control features and feedback options to the end user. An example of a smart dimmer is described in greater detail in commonly assigned U.S. Pat. No. 5,248,919, issued on Sep. 28, 1993, entitled LIGHTING CONTROL DEVICE, which is herein incorporated by reference in its entirety.

FIG. 1 is a front view of a user interface of a prior art smart dimmer switch 10 for controlling the amount of power delivered from a source of AC power to a lighting load. As shown, the dimmer switch 10 includes a faceplate 12, a bezel 14, an intensity selection actuator 16 for selecting a desired level of light intensity of a lighting load (not shown) controlled by the dimmer switch 10, and a control switch actuator 18. Actuation of the upper portion 16A of the intensity selection actuator 16 increases or raises the light intensity of the lighting load, while actuation of the lower portion 16B of the intensity selection actuator 16 decreases or lowers the light intensity. The intensity selection actuator 16 may control a rocker switch, two separate push switches, or the like. The control switch actuator 18 may control a push switch or any other suitable type of actuator and typically provides tactile and auditory feedback to a user when pressed.

The smart dimmer 10 also includes an intensity level indicator in the form of a plurality of light sources 20, such as light-emitting diodes (LEDs). Light sources 20 may be arranged in an array (such as a linear array as shown) representative of a range of light intensity levels of the lighting load being controlled. The intensity level of the lighting load may range from a minimum intensity level, which is preferably the lowest visible intensity, but which may be zero, or “full off,” to a maximum intensity level, which is typically “full on.” Light intensity level is typically expressed as a percentage of full intensity. Thus, when the lighting load is on, light intensity level may range from 1% to 100%.

By illuminating a selected one of the light sources 20 depending upon light intensity level, the position of the illuminated light source within the array provides a visual indication of the light intensity relative to the range when the lamp or lamps being controlled are on. For example, seven LEDs are illustrated in FIG. 1. Illuminating the uppermost LED in the array will give an indication that the light intensity level is at or near maximum. Illuminating the center LED will give an indication that the light intensity level is at about the midpoint of the range. In addition, when the lamp or lamps being controlled are off, all of the light sources 18 are illuminated at a low level of illumination, while the LED representative of the present intensity level in the on state is illuminated at a higher illumination level. This enables the light source array to be more readily perceived by the eye in a darkened environment, which assists a user in locating the switch in a dark room, for example, in order to actuate the switch to control the lights in the room, and provides sufficient contrast between the level-indicating LED and the remaining LEDs to enable a user to perceive the relative intensity level at a glance.

Touch dimmers (or “zip” dimmers) are known in the art. A touch dimmer generally includes a touch-operated input device, such as a resistive or a capacitive touch pad. The touch-operated device responds to the force and position of a point actuation on the surface of the device and in turn controls the semiconductor switches of the dimmer. An example of a touch dimmer is described in greater detail in commonly-assigned U.S. Pat. No. 5,196,782, issued Mar. 23, 1993, entitled TOUCH-OPERATED POWER CONTROL, the entire disclosure of which is hereby incorporated by reference.

FIG. 2 is a cross-sectional view of a prior art touch-operated device 30, specifically, a membrane voltage divider. A conductive element 32 and a resistive element 34 are co-extensively supported in close proximity by a spacing frame 36. An input voltage, V_(IN), is applied across the resistive element 34 to provide a voltage gradient across its surface. When pressure is applied at a point 38 along the conductive element 32 (by a finger or the like), the conductive element flexes downward and electrically contacts a corresponding point along the surface of the resistive element 34, providing an output voltage, V_(OUT), whose value is between the input voltage V_(IN) and ground. When pressure is released, the conductive element 32 recovers its original shape and becomes electrically isolated from the resistive element 34. The touch-operated device 30 is characterized by a contact resistance R_(CONTACT) between the conductive element 32 and the resistive element 34. The contact resistance R_(CONTACT) is dependent upon the force of the actuation of the touch-operated device 30 and is typically substantially small for a normal actuation force.

FIG. 3 is a perspective view of a user interface of a prior art touch dimmer 40. The dimmer 40 comprises a touch-operated device 30, which is located directly behind a faceplate 42. The faceplate 42 includes a flexible area 44 located directly above the conductive element 32 of the touch-operated device 30 to permit a user to actuate the touch-operated device through the faceplate 42. A conventional phase-control dimming circuit is located within an enclosure 46 and controls the power from a source to a load in accordance with pressure applied to a selectable point on flexible area 44. The faceplate 42 may include optional markings 48, 50, 52 to indicate, respectively, the location of flexible area 44, the lowest achievable intensity level of the load, and location of a “power off” control. An optional LED array 54 provides a visual indication of intensity level of the load. When the load is a light source, there is preferably a linear relationship between the number of illuminated LEDs and the corresponding perceived light level. The flexible area 44 may optionally include a light transmissive area through which LED array 54 is visible.

It is desirable to provide a touch dimmer that is responsive to only the position of an actuation on the operational area, e.g., the flexible area 44 of the touch dimmer 40. However, most prior art touch dimmers are responsive to both the force and the position of a point actuation. For example, when a user lightly presses the touch-operated device 30, i.e., with a low actuation force, the contact resistance R_(CONTACT) is substantially larger than during a normal actuation. Accordingly, the output of the touch-operated device 30 is not representative of the position of the actuation and the dimmer 40 may control the lighting load to an undesired intensity level. Therefore, there is a need for a touch dimmer having an operational area that is not responsive to light touches and is responsive to only the position of a point actuation.

SUMMARY OF THE INVENTION

According to the present invention, a load control device for controlling the amount of power delivered to an electrical load from an AC power source, comprises a semiconductor switch, a controller, a touch sensitive actuator, and a stabilizing circuit. The semiconductor switch is operable to be coupled in series electrical connection between the source and the load, the semiconductor switch having a control input for controlling the semiconductor switch between a non-conductive state and a conductive state. The controller is operatively coupled to the control input of the semiconductor switch for controlling the semiconductor switch between the non-conductive state and the conductive state. The touch sensitive actuator has a touch sensitive front surface responsive to a point actuation characterized by a position and a force. The touch sensitive actuator has an output operatively coupled to the controller for providing a control signal to the controller. The stabilizing circuit is coupled to the output of the touch sensitive actuator. The control signal is responsive only to the position of the point actuation.

According to a second embodiment of the present invention, a load control device for controlling the amount of power delivered to an electrical load from an AC power source, the load control device comprises a semiconductor switch, a controller, a touch sensitive actuator, a usage detection circuit, and a stabilizing circuit. The semiconductor switch is operable to be coupled in series electrical connection between the source and the load. The semiconductor switch has a control input for controlling the semiconductor switch between a non-conductive state and a conductive state. The controller is operatively coupled to the control input of the semiconductor switch for controlling the semiconductor switch between the non-conductive state and the conductive state. The touch sensitive actuator having a touch sensitive front surface responsive to a point actuation characterized by a position and a force, the touch sensitive actuator having an output for providing a control signal. The usage detection circuit is operatively coupled between the output of the touch sensitive actuator and the controller for determining whether the point actuation is presently occurring. The stabilizing circuit is operatively coupled between the output of the touch sensitive actuator and the controller for stabilizing the control signal from the output of the touch sensitive actuator. The controller is responsive to the control signal when the usage detection circuit has determined that the point actuation is presently occurring.

According to another aspect of the present invention, in a control circuit for operating an electrical load in response to an output signal from a touch pad, said touch pad comprising an elongated manually touchable resistive area which produces an output signal at an output terminal, said signal representative of the location at which the touch pad is manually touched, said control circuit including a microprocessor having an input connected to said output signal and producing an output for controlling said load in response to the manual input to said touch pad, the improvement comprising a filter capacitor connected between said output terminal and a ground terminal to define a resistive-capacitive circuit with the resistance of said touch pad, said resistive-capacitive circuit characterized by a time constant and being adapted to prevent large transient voltage changes due to low pressure touches of said touch pad.

Further, in a manually operable control structure for producing an electrical signal dependent on the location at which a touch screen is touched; said control structure comprising a resistive touch screen having a control voltage connected to terminals at its opposite ends and an output terminal which is connected to said touch screen at the location of a local manual pressure applied to said screen by a user; a microprocessor having an input connected to said output terminal and producing an output related to the position at which said screen receives said local manual pressure; the improvement which comprises a filter capacitor connected between said output terminal and a ground terminal and defining an R/C circuit with the resistance of said touch screen between said position at which said screen receives local manual pressure and one of its said terminals.

In addition, the present invention provides a process for generating an operating signal from a resistive touch screen in which an output voltage on a output terminal is related to both the location on the screen area which is touched by a users finger and to the pressure of the touch; said process comprising the production of an x signal in response to the touching of said screen at any location on its surface and the production of a y signal in response to the location at which the screen is touched, and applying said x and y signals to a microprocessor; said microprocessor producing an output signal to a circuit to be controlled only when an x output signal is present and a y output signal is also present at the end of a predetermined sample interval.

Other features and advantages of the present invention will become apparent from the following description of the invention that refers to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a user interface of a prior art dimmer;

FIG. 2 is a cross-sectional view of a prior art touch-operated device;

FIG. 3 is a perspective view of a user interface of a prior art touch dimmer;

FIG. 4A is a perspective view of a touch dimmer according to the present invention;

FIG. 4B is a front view of the touch dimmer of FIG. 4A;

FIG. 5A is a partial assembled sectional view of a bezel and the touch sensitive device of the touch dimmer of FIG. 4A;

FIG. 5B is a partial exploded sectional view of the bezel and the touch sensitive device of FIG. 5A;

FIG. 6 shows the force profiles of the components and a cumulative force profile of the touch dimmer of FIG. 4A;

FIG. 7 is a simplified block diagram of the touch dimmer of FIG. 4A;

FIG. 8 is a simplified schematic diagram of a stabilizing circuit and a usage detection circuit of the touch dimmer of FIG. 7 according to a first embodiment of the present invention;

FIG. 9 is a simplified schematic diagram of an audible sound generator of the touch dimmer of FIG. 7;

FIG. 10 is a flowchart of a touch dimmer procedure executed by a controller of the dimmer of FIG. 4A;

FIG. 11 is a flowchart of an Idle procedure of the touch dimmer procedure of FIG. 10;

FIGS. 12A and 12B are flowcharts of an ActiveHold procedure of the touch dimmer procedure of FIG. 10;

FIG. 13 is a flowchart of a Release procedure of the touch dimmer procedure of FIG. 10;

FIGS. 14A and 14B are simplified schematic diagrams of the circuitry for a four wire touch sensitive device and a controller of the touch dimmer of FIG. 4A according to a second embodiment of the present invention;

FIG. 15A is a simplified schematic diagram of the circuitry for a four wire touch sensitive device and a controller of the touch dimmer of FIG. 4A according to a third embodiment of the present invention;

FIG. 15B is a simplified block diagram of a dimmer according to a fourth embodiment of the present invention;

FIG. 15C is a simplified schematic diagram of the circuitry for a three-wire touch sensitive device and a controller of the dimmer of FIG. 15B.

FIG. 16A is a perspective view of a touch dimmer according to a fifth embodiment of the present invention;

FIG. 16B is a front view of the touch dimmer of FIG. 16A;

FIG. 17A is a bottom cross-sectional view of the touch dimmer of FIG. 16B;

FIG. 17B is an enlarged partial view of the bottom cross-sectional view of FIG. 17A;

FIG. 18A is a left side cross-sectional view of the touch dimmer of FIG. 16B;

FIG. 18B is an enlarged partial view of the left side cross-sectional view FIG. 18A;

FIG. 19 is a perspective view of a display printed circuit board of the dimmer of FIG. 16A; and

FIG. 20 is an enlarged partial bottom cross-sectional view of a thin touch sensitive actuator according to a sixth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The foregoing summary, as well as the following detailed description of the preferred embodiments, is better understood when read in conjunction with the appended drawings. For the purposes of illustrating the invention, there is shown in the drawings an embodiment that is presently preferred, in which like numerals represent similar parts throughout the several views of the drawings, it being understood, however, that the invention is not limited to the specific methods and instrumentalities disclosed.

FIGS. 4A and 4B are a perspective view and a front view, respectively, of a touch dimmer 100 according to the present invention. The dimmer 100 includes a faceplate 102, i.e., a cover plate, having a planar front surface 103 and an opening 104. The opening 104 may define a standard industry-defined opening, such as a traditional opening or a decorator opening, or another uniquely-sized opening as shown in FIG. 4A. A bezel 106 having a planar touch sensitive front surface 108 extends through the opening 104 of the faceplate 102. The front surface 108 of the bezel 106 is positioned immediately above a touch sensitive device 110 (shown in FIGS. 5A and 5B), i.e., a touch sensitive element, such that a user of the dimmer 100 actuates the touch sensitive element 110 by pressing the front surface 108 of the bezel 106. As shown in FIG. 4A, the front surface 108 of the bezel 106 is substantially flush with the front surface 103 of the faceplate 102, i.e., the plane of the front surface 108 of the bezel 106 is coplanar with the plane of the front surface 103 of the faceplate 102. However, the bezel 106 may extend through the opening 104 of the faceplate 102 such that the front surface 108 of the bezel is provided in a plane above the plane of the front surface 103 of the faceplate 102. The faceplate 102 is connected to an adapter 109, which is connected to a yoke (not shown). The yoke is adapted to mount the dimmer 100 to a standard electrical wallbox.

The dimmer 100 further comprises a visual display, e.g., a plurality of status markers 112 provided in a linear array along an edge of the front surface 108 of the bezel 106. The status markers 112 are preferably illuminated from behind by status indicators 114, e.g., light-emitting diodes (LEDs), located internal to the dimmer 100 (see FIG. 7). The dimmer 100 preferably comprises a light pipe (not shown) having a plurality of light conductors to conduct the light from the status indicators 114 inside the dimmer to the markers 112 on the front surface 108 of the bezel 106. The status indicators 114 behind the markers 112 are preferably blue. As shown in FIGS. 4A and 4B, the dimmer 100 comprises seven (7) status markers 112. However, the dimmer 100 may comprise any number of status markers. Further, the status markers 112 may be disposed in a vertical linear array along the center of the front surface 108 of the bezel 106. The markers 112 may comprise shadows apparent on the front surface 108 due to voids behind the front surface.

The front surface 108 of the bezel 106 further includes an icon 116. The icon 116 may be any sort of visual marker, such as, for example, a dot. Upon actuation of the lower portion of the front surface 108 surrounding the icon 116, the dimmer 100 causes a connected lighting load 208 (FIG. 7) to change from on to off (and vice versa), i.e., to toggle. Preferably, a blue status indicator and an orange status indicator are located immediately behind the icon 116, such that the icon 116 is illuminated with blue light when the lighting load 208 is on and illuminated with orange light when the lighting load is off. Actuation of the upper portion of the front surface 108, i.e., above the portion surrounding the icon 116, causes the intensity of the lighting load 208 to change. The status indicators 114 behind the status markers 112 are illuminated to display the intensity of the lighting load 208. For example, if the lighting load 208 is at 50% lighting intensity, the middle status indicator will be illuminated. Preferably, the dimmer 100 does not respond to actuations in a keepout region 118 of the front surface 108. The keepout region 118 prevents inadvertent actuation of an undesired portion of the front surface 108 during operation of the dimmer 100.

The dimmer 100 further includes an airgap switch actuator 119. Pulling the airgap switch actuator 119 opens a mechanical airgap switch 219 (FIG. 7) inside the dimmer 100 and disconnects the lighting load 208 from a connected AC voltage source 204 (FIG. 7). The airgap switch actuator 119 extends only sufficiently above the front surface 103 of the faceplate 102 to be gripped by a fingernail of a user. The electronic circuitry of the dimmer 100 (to be described in greater detail below) is mounted on a printed circuit board (PCB) (not shown). The PCB is housed in an enclosure (not shown), i.e., an enclosed volume, which is attached to the yoke of the dimmer 100.

FIG. 5A is a partial assembled sectional view and FIG. 5B is a partial exploded sectional view of the bezel 108 and the touch sensitive device 110 of the dimmer 100 according to the present invention. The touch sensitive device 110 comprises, for example, a resistive divider, and operates in a similar fashion as the touch-operated device 30 of the prior art touch dimmer 40. The touch sensitive device 110 includes a conductive element 120 and a resistive element 122 supported by a spacing frame 124. However, the touch sensitive device 110 may comprise a capacitive touch screen or any other type of touch responsive element. Such touch sensitive devices are often referred to as touch pads or touch screens.

An elastomer 126 is received by an opening 128 in the rear surface of the bezel 106. The elastomer 126 is positioned between the bezel 106 and the touch sensitive device 110, such that a press on the front surface 108 of the bezel is transmitted to the conductive element 120 of the touch sensitive device 110. Preferably, the elastomer 126 is made of rubber and is 0.040″ thick. The elastomer 126 preferably has a durometer of 40 A, but may have a durometer in the range of 20 A to 80 A. The conductive element 120 and the resistive element 122 of the touch sensitive device 110 and the elastomer 126 are preferably manufactured from a transparent material such that the light from the plurality of status indicators 114 inside the dimmer 100 are operable to shine through the touch sensitive device 110 and the elastomer 126 to front surface 108 of the bezel 106.

The position and size of the touch sensitive device 110 is demonstrated by the dotted line in FIG. 4B. The touch sensitive device 110 has a length L₁ and a width W₁ that is larger than a length L₂ and a width W₂ of the front surface 108 of the bezel 106. Accordingly, a first area A₁ of the surface of touch sensitive device 110 (i.e., A₁=L₁·W₁) is greater than a second area A₂ of the front surface 108 of the bezel 106 (i.e., A₂=L₂·W₂). An orthogonal projection of the second area A₂ onto the first area A₁ is encompassed by the first area A₁, such that a point actuation at any point on the front surface 108 of the bezel 106 is transmitted to the conductive element 120 of the touch sensitive device 110. As shown in FIGS. 4A and 4B, the length L₂ of the front surface 108 of the bezel 106 is approximately four (4) times greater than the width W₂. Preferably, the length L₂ of the front surface 108 of the bezel 106 is four (4) to six (6) times greater than the width W₂. Alternatively, the front surface 108 of the bezel 106 may be provided in an opening of a decorator-style faceplate

FIG. 6 shows the force profiles of the components of the dimmer 100 shown in FIGS. 5A and 5B and a cumulative force profile for the touch sensitive device 110 of the dimmer 100. Each of the force profiles shows the force required to actuate the touch sensitive device 110 with respect to the position of the point actuation. The force profile represents the amount of force required to displace the element by a given amount. While the force profiles in FIG. 6 are shown with respect to the widths of the components of the dimmer 100, a similar force profile is also provided along the length of the components.

FIG. 6( a) shows a force profile of the bezel 106. The bezel 106 has substantially thin sidewalls 129, e.g., 0.010″ thick, such that the bezel 106 exhibits a substantially flat force profile. FIG. 6( b) shows a force profile of the touch sensitive device 110. The force required to actuate the touch sensitive device 110 increases near the edges because of the spacing frames 124. FIG. 6( c) shows a force profile of the elastomer 126. The force profile of the elastomer 126 is substantially flat, i.e., a force at any point on the front surface of the elastomer 126 will result in a substantially equal force at the corresponding point on the rear surface.

FIG. 6( d) is a total force profile of the touch dimmer 100. The individual force profiles shown in FIGS. 6( a)-6(c) are additive to create the total force profile. The total force profile is substantially flat across the second area A₂ of the front surface 108 of the bezel 106. This means that a substantially equal minimum actuation force f_(MIN) is required to actuate the touch sensitive device 110 at all points of the front surface 108 of the bezel 106, even around the edges. Accordingly, the dimmer 100 of the present invention provides a maximum operational area in an opening of a faceplate, i.e., substantially all of the second area A₂ of the front surface 108 of the bezel 106, which is an improvement over the prior art touch dimmers. The minimum actuation force f_(MIN) is substantially equal at all points on the front surface 108 of the bezel 106. For example, the minimum actuation force f_(MIN) may be 20 grams.

FIG. 7 is a simplified block diagram of the touch dimmer 100 according to the present invention. The dimmer 100 has a hot terminal 202 connected to an AC voltage source 204 and a dimmed hot terminal 206 connected to a lighting load 208. The dimmer 100 employs a bidirectional semiconductor switch 210 coupled between the hot terminal 202 and the dimmed hot terminal 206, to control the current through, and thus the intensity of, the lighting load 208. The semiconductor switch 210 has a control input (or gate), which is connected to a gate drive circuit 212. The input to the gate renders the semiconductor switch 210 selectively conductive or non-conductive, which in turn controls the power supplied to the lighting load 208. The gate drive circuit 212 provides a control input to the semiconductor switch 210 in response to a control signal from a controller 214. The controller 214 may be any suitable controller, such as a microcontroller, a microprocessor, a programmable logic device (PLD), or an application specific integrated circuit (ASIC).

A zero-crossing detect circuit 216 determines the zero-crossing points of the AC source voltage from the AC power supply 204. A zero-crossing is defined as the time at which the AC supply voltage transitions from positive to negative polarity, or from negative to positive polarity, at the beginning of each half-cycle. The zero-crossing information is provided as an input to the controller 214. The controller 214 generates the gate control signals to operate the semiconductor switch 210 to thus provide voltage from the AC power supply 204 to the lighting load 208 at predetermined times relative to the zero-crossing points of the AC waveform. A power supply 218 generates a direct-current (DC) voltage V_(CC), e.g., 5 volts, to power the controller 214 and other low voltage circuitry of the dimmer 100.

The touch sensitive device 110 is coupled to the controller 214 through a stabilizing circuit 220 and a usage detection circuit 222. The stabilizing circuit 220 is operable to stabilize the voltage output of the touch sensitive device 110. Accordingly, the voltage output of the stabilizing circuit 220 is not dependent on the magnitude of the force of the point actuation on the touch sensitive device 110, but rather is dependent solely on the position of the point actuation. The usage detection circuit 222 is operable to detect when a user is actuating the front surface 108 of the dimmer 100. The controller 214 is operable to couple and decouple the stabilizing circuit 220 and the usage detection circuit 222 from the output of the touch sensitive device 110. The controller is further operable to receive control signals from both the stabilizing circuit 220 and the usage detection circuit 222. Preferably, the stabilizing circuit 220 has a slow response time, while the usage detection circuit 222 has a fast response time. Thus, the controller 214 is operable to control the semiconductor switch 210 in response to the control signal provided by the stabilizing circuit 220 when the usage detection circuit 222 has detected an actuation of the touch sensitive device 110.

The controller 214 is operable to drive the plurality of status indicators 114, e.g., light-emitting diodes (LEDs), which are located behind the markers 112 on the front surface 108 of the dimmer 100. The status indicators 114 also comprise the blue status indicator and the orange status indicator that are located immediately behind the icon 116. The blue status indicator and the orange status indicator may be implemented as separate blue and orange LEDs, respectively, or as a single bi-colored LED.

The dimmer 100 further comprises an audible sound generator 224 coupled to the controller 214, such that the controller is operable to cause the sound generator to produce an audible sound in response to an actuation of the touch sensitive device 110. A memory 225 is coupled to the controller 214 and is operable to store control information of the dimmer 100.

FIG. 8 is a simplified schematic diagram of the circuitry for the touch sensitive device 110 and the controller 214, i.e., the stabilizing circuit 220 and the usage detection circuit 222, according to a first embodiment of the present invention. The resistive element 122 of the touch sensitive device 110 is coupled between the DC voltage V_(CC) of the power supply 218 and circuit common, such that the DC voltage V_(CC) provides a biasing voltage to the touch sensitive device. For example, the resistive element 122 may have a resistance R_(E) of 7.6 kΩ. The position of contact between the conductive element 120 and the resistive element 122 of the touch sensitive device 110 is determined by the position of a point actuation on the front surface 108 of the bezel 106 of the dimmer 100. The conductive element 120 is coupled to both the stabilizing circuit 220 and the usage detection circuit 222. As shown in FIG. 7, the touch sensitive device 110 of the dimmer 100 of the first embodiment is a three-wire device, i.e., the touch sensitive device has three connections or electrodes. The touch sensitive device provides one output that is representative of the position of the point actuation along a Y-axis, i.e., a longitudinal axis of the dimmer 100 as shown in FIG. 4B.

The stabilizing circuit 220 comprises a whacking-grade capacitor C230 (that is, a capacitor having a large value of capacitance) and a first switch 232. The controller 214 is operable to control the first switch 232 between a conductive state and a non-conductive state. When the first switch 232 is conductive, the capacitor C230 is coupled to the output of the touch sensitive device 110, such that the output voltage is filtered by the capacitor C230. When a touch is present, the voltage on the capacitor C230 will be forced to a steady-state voltage representing the position of the touch on the front surface 108. When no touch is present, the voltage on the capacitor will remain at a voltage representing the position of the last touch. The touch sensitive device 110 and the capacitor C230 form a sample-and-hold circuit. The response time of the sample-and-hold circuit is determined by a resistance R_(D) of the touch sensitive device (i.e., the resistance R_(E) of the resistive element and a contact resistance R_(C)) and the capacitance of the capacitor C230. During typical actuation, the contact resistance R_(c) is small compared to the value of R_(E), such that a first charging time constant τ₁ is approximately equal to R_(E)·C₂₃₀. This time constant τ₁ is preferably 13 ms, but may be anywhere between 6 ms and 15 ms.

When a light or transient press is applied to the touch sensitive device 110, the capacitor C230 will continue to hold the output at the voltage representing the position of the last touch. During the release of the touch sensitive device 110, transient events may occur that produce output voltages that represent positions other than the actual touch position. Transient presses that are shorter than the first charging time constant τ₁ will not substantially affect the voltage on the capacitor C230, and therefore will not substantially affect the sensing of the position of the last actuation. During a light press, a second charging time constant τ₂ will be substantially longer than during normal presses, i.e., substantially larger than the first time constant τ₁, due to the higher contact resistance R_(C). However, the steady-state value of the voltage across the capacitor C230 will be the same as for a normal press at the same position. Therefore, the output of the stabilizing circuit 220 is representative of only the position of the point of actuation of the touch sensitive device 110.

The usage detection circuit 222 comprises a resistor R234, a capacitor C236, and a second switch 238, which is controlled by the controller 214. When the switch 238 is conductive, the parallel combination of the resistor R234 and the capacitor C236 is coupled to the output of the touch sensitive device 110. Preferably, the capacitor C236 has a substantially small capacitance C₂₃₆, such that the capacitor C236 charges substantially quickly in response to all point actuations on the front surface 108. The resistor R234 allows the capacitor C236 to discharge quickly when the switch 238 is non-conductive. Therefore, the output of the usage detection circuit 222 is representative of the instantaneous usage of the touch sensitive device 110.

The controller 214 controls the switches 232, 238 in a complementary manner. When the first switch 232 is conductive, the second switch 238 is non-conductive, and vice versa. The controller 214 controls the second switch 238 to be conductive for a short period of time t_(USAGE) once every half cycle of the voltage source 204 to determine whether the user is actuating the front surface 108. Preferably, the short period of time t_(USAGE) is approximately 100 μsec or 1% of the half-cycle (assuming each half-cycle is 8.33 msec long). For the remainder of the time, the first switch 232 is conductive, such that the capacitor C230 is operable to charge accordingly. When the first switch 232 is non-conductive and the second switch 238 is conductive, the whacking-grade capacitor C230 of the stabilizing circuit 220 is unable to discharge at a significant rate, and thus the voltage developed across the capacitor C230 will not change significantly when the controller 214 is determining whether the touch sensitive device 110 is being actuated through the usage detection circuit 222. While the stabilizing circuit 220 is shown and described as a hardware circuit in the present application, the controller 214 could alternatively provide the filtering functionality of the stabilizing circuit entirely in software.

FIG. 9 is a simplified schematic diagram of the audible sound generator 224 of the dimmer 100. The audible sound generator 224 uses an audio power amplifier integrated circuit (IC) 240, for example, part number TPA721 manufactured by Texas Instruments, Inc., to generate a sound from a piezoelectric or magnetic speaker 242. The amplifier IC 240 is coupled to the DC voltage V_(CC) (pin 6) and circuit common (pin 7) to power the amplifier IC. A capacitor C244 (preferably having a capacitance of 0.1 μF) is coupled between the DC voltage V_(CC) and circuit common to decouple the power supply voltage and to ensure the output total harmonic distortion (THD) is as low as possible.

The audible sound generator 224 receives a SOUND ENABLE signal 246 from the controller 214. The SOUND ENABLE signal 246 is provided to an enable pin (i.e., pin 1) on the amplifier IC 240, such that the audible sound generator 224 will be operable to generate the sound when the SOUND ENABLE signal is at a logic high level.

The audible sound generate 224 further receives a SOUND WAVE signal 248 from the controller 214. The SOUND WAVE signal 248 is an audio signal that is amplified by the amplifier IC 240 to generate the appropriate sound at the speaker 242. The SOUND WAVE signal 248 is first filtered by a low-pass filter comprising a resistor R250 and a capacitor C252. Preferably, the resistor R250 has a resistance of 1 kΩ and the capacitor C252 has a capacitance of 0.1 nF. The filtered signal is then passed through a capacitor C254 to produce an input signal V_(IN). The capacitor C254 allows the amplifier IC to bias the input signal V_(IN) to the proper DC level for optimum operation and preferably has a capacitance of 0.1 μF. The input signal V_(IN) is provided to a negative input (pin 4) of the amplifier IC 240 through a input resistor R_(I). A positive input (pin 3) of the amplifier IC 240 and with a bypass pin (pin 2) are coupled to circuit common through a bypass capacitor C256 (preferably, having a capacitance of 0.1 μF).

The output signal V_(OUT) of the amplifier IC 240 is produced from a positive output (pin 5) to a negative output (pin 8) and is provided to the speaker 242. The negative input (pin 4) is coupled to the positive output (pin 5) through an output resistor R_(F). The gain of the amplifier IC 240 is set by the input resistor R_(I) and the feedback resistor R_(F), i.e., Gain=V _(OUT) /V _(IN)=−2·(R _(F) /R _(I)). Preferably, the input resistor R_(I) and the output resistor R_(F) both have resistances of 10 kΩ, such that the gain of the amplifier IC 240 is negative two (−2).

FIG. 10 is a flowchart of a touch dimmer procedure 300 executed by the controller 214 of the dimmer 100 according to the present invention. Preferably, the touch dimmer procedure 300 is called from the main loop of the software of the controller 214 once every half cycle of the AC voltage source 204. The touch dimmer procedure 300 selectively executes one of three procedures depending upon the state of the dimmer 100. If the dimmer 100 is in an “Idle” state (i.e., the user is not actuating the touch sensitive device 110) at step 310, the controller 214 executes an Idle procedure 400. If the dimmer 100 is in an “ActiveHold” state (i.e., the user is presently actuating the touch sensitive device 110) at step 320, the controller 214 executes an ActiveHold procedure 500. If the dimmer 100 is in a “Release” state (i.e., the user has recently ceased actuating the touch sensitive device 110) at step 330, the controller 214 executes a Release procedure 600.

FIG. 11 is a flowchart of the Idle procedure 400 according to the present invention. The controller 114 uses a “sound flag” and a “sound counter” to determine when to cause the audible sound generator 224 to generate the audible sound. The purpose of the sound flag is to cause the sound to be generated the first time that the controller 214 executes the ActiveHold procedure 500 after being in the Idle state. If the sound flag is set, the controller 214 will cause the sound to be generated. The sound counter is used to ensure that the controller 214 does not cause the audible sound generator 224 to generate the audible sound too often. The sound counter preferably has a maximum sound counter value S_(MAX), e.g., approximately 425 msec. Accordingly, there is a gap of approximately 425 msec between generations of the audible sound. The sound counter is started during the Release procedure 600 as will be described in greater detail below. Referring to FIG. 11, upon entering the Idle state, the controller 214 sets the sound flag at step 404 if the sound flag is not set at step 402.

An “LED counter” and an “LED mode” are used by the controller 214 to control the status indicators 114 (i.e., the LEDs) of the dimmer 100. The controller 214 uses the LED counter to determine when a predetermined time t_(LED) has expired since the touch sensitive device 110 was actuated. When the predetermined time t_(LED) has expired, the controller 214 will change the LED mode from “active” to “inactive”. When the LED mode is “active”, the status indicators 114 are controlled such that one or more of the status indicators are illuminated to a bright level. When the predetermined time t_(LED) expires, the LED mode is changed to “inactive”, i.e., the status indicators 114 are controlled such that one or more of the status indicators are illuminated to a dim level. Referring to FIG. 11, if the LED counter is less than a maximum LED counter value L_(MAX) at step 410, the LED counter is incremented at step 412 and the process moves on to step 418. However, if the LED counter is not less than the maximum LED counter value L_(MAX), the LED counter is cleared at step 414 and the LED mode is set to inactive at step 416. Since the touch dimmer procedure 300 is executed once every half cycle, the predetermined time t_(LED) is preferably equal to t _(LED) =T _(HALF) ·L _(MAX), where T_(HALF) is the period of a half cycle.

Next, the controller 214 reads the output of the usage detection circuit 222 to determine if the touch sensitive device 110 is being actuated. Preferably, the usage detection circuit 222 is monitored once every half cycle of the voltage source 204. At step 418, the controller 214 opens switch 232 and closes switch 238 to couple the resistor R234 and the capacitor C236 to the output of the touch sensitive device 110. The controller 214 determines the DC voltage of the output of the usage detection circuit 222 at step 420, preferably, by using an analog-to-digital converter (ADC). Next, the controller 214 closes switch 232 and opens switch 238 at step 422.

At step 424, if there is activity on the front surface 108 of the dimmer 100, i.e., if the DC voltage determined at step 420 is above a predetermined minimum voltage threshold, then an “activity counter” is incremented at step 426. Otherwise, the activity counter is cleared at step 428. The activity counter is used by the controller 214 to determine if the DC voltage determined at step 420 is the result of a point actuation of the touch sensitive device 110 rather than noise or some other undesired impulse. The use of the activity counter is similar to a software “debouncing” procedure for a mechanical switch, which is well known in the art. If the activity counter is not less than a maximum activity counter value A_(MAX) at step 430, then the dimmer state is set to the ActiveHold state at step 432. Otherwise, the process simply exits at step 434.

FIGS. 12A and 12B are flowcharts of the ActiveHold procedure 500, which is executed once every half cycle when the touch sensitive device 110 is being actuated, i.e., when the dimmer 100 is in the ActiveHold state. First, a determination is made as to whether the user has stopped using, i.e., released, the touch sensitive device 110. The controller 214 opens switch 232 and closes switch 238 at step 510, and reads the output of the usage detection circuit 222 at step 512. At step 514, the controller 214 closes switch 232 and opens switch 238. If there is no activity on the front surface 108 of the dimmer 100 at step 516, the controller 214 increments an “inactivity counter” at step 518. The controller 214 uses the inactivity counter to make sure that the user is not actuating the touch sensitive device 110 before entering the Release mode. If the inactivity counter is less than a maximum inactivity counter value I_(MAX) at step 520, the process exits at step 538. Otherwise, the dimmer state is set to the Release state at step 522, and then the process exits.

If there is activity on the touch sensitive device 110 at step 516, the controller 214 reads the output of the stabilizing circuit 220, which is representative of the position of the point actuation on the front surface 108 of the dimmer 100. Since the switch 232 is conductive and the switch 238 is non-conductive, the controller 214 determines the DC voltage at the output of the stabilizing circuit 220, preferably using an ADC, at step 524.

Next, the controller 214 uses a buffer to “filter” the output of stabilizing circuit 220. When a user actuates the touch sensitive device 110, the capacitor C230 will charge to approximately the steady-state voltage representing the position of the actuation on the front surface 108 across a period of time determined by the first time constant τ₁ as previously described. Since the voltage across the capacitor C230, i.e., the output of the stabilizing circuit 220, is increasing during this time, the controller 214 delays for a predetermined period of time at step 525, preferably, for approximately three (3) half cycles.

When a user's finger is removed from the front surface 108 of the bezel 106, subtle changes in the force and position of the point actuation occur, i.e., a “finger roll-off” event occurs. Accordingly, the output signal of the touch sensitive device 110 is no longer representative of the position of the point actuation. To prevent the controller 214 from processing reads during a finger roll-off event, the controller 214 saves the reads in the buffer and processes the reads with a delay, e.g., six half cycles later. Specifically, when the delay is over at step 525, the controller 214 rotates the new read (i.e., from step 524) into the buffer at step 526. If the buffer has at least six reads at step 528, the controller 214 averages the reads in the fifth and sixth positions in the buffer at step 530 to produce the touch position data. In this way, when the user stops actuating the touch sensitive device 110, the controller 214 detects this change at step 516 and sets the dimmer state to the Release state at step 522 before the controller processes the reads saved in the buffer near the transition time of the touch sensitive device.

At step 532, the controller 114 determines if the touch position data from step 530 is in the keepout region 118 (as shown in FIG. 4B). If the touch position data is in the keepout region 118, the ActiveHold procedure 500 simply exits at step 538. Otherwise, a determination is made at step 534 as to whether the sound should be generated. Specifically, if the sound flag is set and if the sound counter has reached a maximum sound counter value S_(MAX), the controller 214 drives the SOUND ENABLE signal 246 high and provides the SOUND WAVE signal 248 to the audible sound generator 224 to generate the sound at step 535. Further, the sound flag is cleared at step 536 such that the sound will not be generated as long as the dimmer 100 remains in the ActiveHold state.

If the touch position data is in the toggle area, i.e., the lower portion of the front surface 108 of the bezel 106 surrounding the icon 116 (as shown in FIG. 4A), at step 540, the controller 214 processes the actuation of the touch sensitive device 110 as a toggle. If the lighting load 208 is presently off at step 542, the controller 214 turns the lighting load on. Specifically, the controller 214 illuminates the icon 116 with the blue status indicator at step 544 and dims the lighting load 208 up to the preset level, i.e., the desired lighting intensity of the lighting load, at step 546. If the lighting load is presently on at step 542, the controller 214 turns on the orange status indicator behind the icon 116 at step 548 and fades the lighting load 208 to off at step 550.

If the touch position data is not in the toggle area at step 540, the controller 214 scales the touch position data at step 552. The output of the stabilizing circuit 220 is a DC voltage between a maximum value, i.e., substantially the DC voltage V_(CC), and a minimum value, which corresponds to the DC voltage providing by the touch sensitive device 110 when a user is actuating the lower end of the upper portion of the front surface 108 of the bezel 106. The controller 214 scales this DC voltage to be a value between off (i.e., 1%) and full intensity (i.e., 100%) of the lighting load 208. At step 554, the controller 214 dims the lighting load 208 to the scaled level produced in step 552.

Next, the controller 214 changes the status indicators 114 located behind the markers 112 on the front surface 108 of the bezel 106. As a user actuates the touch sensitive device 110 to change intensity of the lighting load 208, the controller 214 decides whether to change the status indicator 114 that is presently illuminated. Since there are seven (7) status indicators to indicate an intensity between 1% and 100%, the controller 214 may illuminate the first status indicator, i.e., the lowest status indicator, to represent an intensity between 1% and 14%, the second status indicator to represent an intensity between 15% and 28%, and so on. The seventh status indicator, i.e., the highest status indicator, may be illuminated to represent an intensity between 85% and 100%. Preferably, the controller 214 uses hysteresis to control the status indicators 114 such that if the user actuates the front surface 108 at a boundary between two of the regions of intensities described above, consecutive status indicators do not toggle back and forth.

Referring to FIG. 12B, a determination is made as to whether a change is needed as to which status indicator is illuminated at step 556. If the present LED (in result to the touch position data from step 530) is the same as the previous LED, then no change in the LED is required. The present LED is set the same as the previous LED at step 558, a hysteresis counter is cleared at step 560, and the process exits at step 570.

If the present LED is not the same as the previous LED at step 556, the controller 214 determines if the LED should be changed. Specifically, at step 562, the controller 214 determines if present LED would change if the light level changed by 2% from the light level indicated by the touch position data. If not, the hysteresis counter is cleared at step 560 and the process exits at step 570. Otherwise, the hysteresis counter is incremented at step 564. If the hysteresis counter is less than a maximum hysteresis counter value H_(MAX) at step 566, the process exits at step 570. Otherwise, the LEDs are changed accordingly based on the touch position data at step 568.

FIG. 13 is a flowchart of the Release procedure 600, which is executed after the controller 214 sets the dimmer state to the Release state at step 522 of the ActiveHold procedure 500. First, a save flag is set at step 610. Next, the sound counter is reset at step 612 to ensure that the sound will not be generated again, e.g., for preferably 18 half cycles. At step 618, a determination is made as to whether the dimmer 100 is presently executed a fade-to-off. If not, the present level is saved as the preset level in the memory 225 at step 620. Otherwise, the desired lighting intensity is set to off at step 622, the long fade countdown in started at step 624, and the preset level is saved as off in the memory 225.

FIG. 14A and FIG. 14B are simplified schematic diagrams of the circuitry for a four-wire touch sensitive device 710 and a controller 714 according to a second embodiment of the present invention. The four-wire touch sensitive device 710 has four connections, i.e., electrodes, and provides two outputs: a first output representative of the position of a point actuation along the Y-axis, i.e., the longitudinal axis of the dimmer 100 a shown in FIG. 4B, and a second output representative of the position of the point actuation along the X-axis, i.e., an axis perpendicular to the longitudinal axis. The four-wire touch sensitive device 710 provides the outputs depending on how the DC voltage V_(CC) is connected to the touch sensitive device. A stabilizing circuit 720 is operatively coupled to the first output and a usage detection circuit 722 is operatively coupled to the second output.

The controller 714 controls three switches 760, 762, 764 to connect the touch sensitive device 710 to the DC voltage V_(CC) accordingly. When the switches 760, 762, 764 are connected in position A as shown in FIG. 14A, the DC voltage V_(CC) is coupled across the Y-axis resistor, and the X-axis resistor provides the output to the stabilizing circuit 720. When the switches 760, 762, 764 are connected in position B as shown in FIG. 14B, the DC voltage V_(CC) is coupled across the X-axis resistor, and the Y-axis resistor provides the output to the usage detection circuit 722. Since the controller 714 provides one output signal to control whether the stabilizing circuit 720 or the usage detection circuit 722 is coupled to the touch sensitive device 110, the software executed by the controller 714 is the same as the software executed by the controller 214 shown in FIGS. 10-13.

FIG. 15A is a simplified schematic diagram of the circuitry for the four-wire touch sensitive device 710 and a controller 814 according to a third embodiment of the present invention. The controller 814 is operable to read the position of a point actuation on the four-wire touch sensitive device 710 along both the Y-axis and the X-axis. When determining the position along the Y-axis, the controller 814 operates the same as the controller 714 shown in FIGS. 14A and 14B by controlling the switches 760, 762, 764 as described above.

An additional stabilizing circuit 870 is provided for determining the position of the point actuation along the X-axis. The additional stabilizing circuit 870 comprises a whacking-grade capacitor C872. The controller 814 controls a switch 874 to selectively switch the output of the X-axis between the usage detection circuit 722 and the additional stabilizing circuit 870. The controller 814 controls the switch 874 in a similar fashion to how the controller 214 controls the switches 232, 238 (as shown in FIG. 8).

FIG. 15B is a simplified block diagram of a dimmer 1000 according to a fourth embodiment of the present invention. FIG. 15C is a simplified schematic diagram of the circuitry for the three-wire touch sensitive device 110 and a controller 1014 of the dimmer 1000 according to the fourth embodiment. The dimmer 1000 comprises only a stabilizing circuit 1020 and does not comprise a usage detection circuit. The stabilizing circuit 1020 only comprises a whacking-grade capacitor C1030. Accordingly, the controller 1014 is not operable to control the stabilizing circuit 1020 and is responsive to the touch sensitive device 100 through only the stabilizing circuit.

FIGS. 16A and 16B are a perspective view and a front view, respectively, of a touch dimmer 900 according to a fifth embodiment of the present invention. FIG. 17A is a bottom cross-sectional view and FIG. 17B is an enlarged partial bottom cross-sectional view of the dimmer 900. FIG. 18A is a left side cross-sectional view and FIG. 18B is an enlarged partial left side cross-sectional view of the dimmer 900.

The touch dimmer 900 includes a thin touch sensitive actuator 910 comprising an actuation member 912 extending through a bezel 914. The dimmer 900 further comprises a faceplate 916, which has a non-standard opening 918 and mounts to an adapter 920. The bezel 914 is housed behind the faceplate 916 and extends through the opening 918. The adapter 920 connects to a yoke 922, which is adapted to mount the dimmer 900 to a standard electrical wallbox. A main printed circuit board (PCB) 924 is mounted inside an enclosure 926 and includes the some of the electrical circuitry of the dimmer 200, e.g., the semiconductor switch 210, the gate drive circuit 212, the controller 214, the zero-crossing detect circuit 216, the power supply 218, the stabilizing circuit 220, the usage detection circuit 222, the audible sound generator 224, and the memory 225, of the dimmer 200. The thin touch sensitive actuator 910 preferably extends beyond the faceplate by 1/16″, i.e., has a height of 1/16″, but may have a height in the range of 1/32″ to 3/32″. Preferably, the touch sensitive actuator 910 has a length of 3⅝″ and a width of 3/16″. However, the length and the width of the touch sensitive actuator 910 may be in the ranges of 2⅝″-4″ and ⅛″-¼″, respectively.

The touch sensitive actuator 910 operates to contact a touch sensitive device 930 inside the touch dimmer 900. The touch sensitive device 930 is contained by a base 932. The actuation member 912 includes a plurality of long posts 934, which contact the front surface of the touch sensitive device 930 and are arranged in a linear array along the length of the actuation member. The posts 934 act as force concentrators to concentrate the force from an actuation of the actuation member 912 to the touch sensitive device 930.

A plurality of status indicators 936 are arranged in a linear array behind the actuation member 912. The status indicators are mounted on a display PCB 938, i.e., a status indicator support board, which is mounted between the touch sensitive device 930 and the bezel 914. FIG. 19 is a perspective view of the display PCB 938. The display PCB 938 includes a plurality of holes 939, which the long posts 934 extend through to contact the touch sensitive device 930. The actuation member 912 is preferably constructed from a translucent material such that the light of the status indicators 936 is transmitted to the surface of the actuation member. A plurality of short posts 940 are provided in the actuation member 912 directly above the status indicators 936 to operate as light pipes for the linear array of status indicators. The display PCB 938 comprises a tab 952 having a connector 954 on the bottom side for connecting the display PCB 938 to the main PCB 924.

The actuation member 912 comprises a notch 942, which separates a lower portion 944 and an upper portion 946 of the actuation member. Upon actuation of the lower portion 944 of the actuation member 912, the dimmer 900 causes the connected lighting load to toggle from on to off (and vice versa). Preferably, a blue status indicator 948 and an orange status indicator 950 are located behind the lower portion 944, such that the lower portion is illuminated with blue light when the lighting load is on and illuminated with orange light with the lighting load is off. Actuation of the upper portion 946 of the actuation member 912, i.e., above the notch 942, causes the intensity of the lighting load to change to a level responsive to the position of the actuation on the actuation member 912. The status indicators 936 behind the status markers 112 are illuminated to display the intensity of the lighting load as with the previously-discussed touch dimmer 100.

FIG. 20 is an enlarged partial bottom cross-sectional view of a thin touch sensitive actuator 960 according to a sixth embodiment of the present invention. The touch sensitive actuator 960 comprises an actuation member 962 having two posts 964 for actuating the touch sensitive device 930. A plurality of status indicators 966 are mounted on a flexible display PCB 968, i.e., a flexible status indicator support board, which the posts 964 of the actuation member 962 are operable to actuate the touch sensitive device 930 through. The status indicators 966 are preferably blue LEDs and are arranged along the length of the actuation member 962. Preferably, the actuation member 962 is constructed from a translucent material such that the light of the status indicators 966 is transmitted to the surface of the actuation member.

Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims. 

1. A user interface for a lighting control, the user interface comprising: a touch sensitive front surface having a longitudinal axis and a lateral axis; a four-wire resistive touch pad responsive to a point actuation on the touch sensitive front surface, the resistive touch pad having a longitudinal resistive element for providing a first control signal representative of the position of the point actuation along the longitudinal axis, and a lateral resistive element for providing a second control signal representative of the position of the point actuation along the lateral axis; a controller operable to receive the first and second control signals; a first capacitor adapted to be coupled between the lateral resistive element and a circuit common, the first capacitor operable to charge and discharge through the longitudinal resistive element of the resistive touch pad to stabilize the first control signal; and first, second, and third switches responsive to the controller, each of the switches comprising first, second, and third terminals, and operable to be controlled between a first position in which the first terminal is electrically connected to the second terminal, and a second position in which the first terminal is electrically connected to the third terminal, the switches coupled to the touch sensitive device, such that when the controller controls all of the switches to the first position, a DC supply voltage is coupled across the longitudinal resistive element, the controller is coupled to the lateral resistive element, and the first capacitor is coupled between the lateral resistive element and the circuit common, and when the controller controls all of the switches to the second position, the DC supply voltage is coupled across the lateral resistive element and the controller is coupled to the longitudinal resistive element; wherein the controller is operable to determine, from the second control signal, if the touch sensitive front surface is presently being actuated, and to determine, from the first control signal, the position of the point actuation along the longitudinal axis.
 2. The user interface of claim 1, further comprising: a second capacitor adapted to be coupled between the longitudinal resistive element and the circuit common, the second capacitor having a capacitance substantially smaller than a capacitance of the first capacitor; and a first resistor adapted to be coupled between the longitudinal resistive element and the circuit common, such that the first resistor is coupled in parallel electrical connection with the second capacitor; wherein when the controller controls all of the switches to the second position, the parallel combination of the second capacitor and the first resistor is coupled between the longitudinal resistive element and the circuit common producing a third control signal between the longitudinal resistive element and the circuit common.
 3. The user interface of claim 2, wherein the controller controls the switches between the first and second positions on a periodic basis, such that the switches are in the first position for a substantially long period of time and in the second position for a substantially short period of time.
 4. The user interface of claim 3, wherein the controller controls the switches between the first and second positions on a periodic basis, such that the switches are in the second position for approximately 1% of the time.
 5. The user interface of claim 4, wherein the lighting control is adapted to be coupled to an AC power source, and the controller controls the switches between the first and second positions on a periodic basis each half-cycle of the AC power source, such that the switches are in the second position for approximately 1% of each half-cycle.
 6. The user interface of claim 2, wherein the resistive touch pad and the first capacitor form a sample-and-hold circuit.
 7. The user interface of claim 6, wherein the time constant of the sample-and-hold circuit ranges from approximately 6 milliseconds to 15 milliseconds.
 8. The user interface of claim 7, wherein the time constant of the sample-and-hold circuit is approximately 13 milliseconds.
 9. The user interface of claim 2, further comprising: a third capacitor adapted to be coupled between the longitudinal resistive element and the controller, the third capacitor adapted to stabilize the second control signal of the resistive touch pad, the second capacitor having a capacitance substantially larger than the capacitance of the second capacitor; wherein the controller is operable to receive the third control signal to determine the position of the point actuation along the longitudinal axis in response to the first control signal, and to determine the position of the point actuation along the lateral axis in response to the second control signal.
 10. The user interface of claim 9, further comprising: a fourth switch comprising first, second, and third terminals, and operable to be controlled between a first position in which the first terminal is electrically connected to the second terminal and a second position in which the first terminal is electrically connected to the third terminal, the fourth switch coupled to the third capacitor, the parallel combination of the second capacitor and the first resistor, and one of the first, second, and third switches, such that when the fourth switch is in the first position, the third capacitor is connected to the longitudinal resistive element of the resistive touch pad, and when the fourth switch is in the second position, the parallel combination of the second capacitor and the first resistor is connected to the longitudinal resistive element of the resistive touch pad; wherein the controller controls the first, second, third, and fourth switches, such that when the fourth switch is in the first position, the controller is operable to determine the position of the point actuation along the lateral axis, and when the fourth switch is in the second position, to determine if the point actuation on the touch sensitive front surface is presently occurring.
 11. A user interface for a lighting control, the user interface comprising: a touch sensitive front surface having a longitudinal axis and a lateral axis; a three-wire resistive touch pad responsive to a point actuation on the touch sensitive front surface, the resistive touch pad having a longitudinal resistive element and an output with a DC supply voltage coupled across the longitudinal resistive element, such that the output is operable to provide an output voltage representative of the position of the point actuation along the longitudinal axis; a controller having first and second inputs; a first capacitor coupled between the first input of the controller and a circuit common, the first capacitor operable to charge and discharge through the longitudinal resistive element of the resistive touch pad to stabilize the first control signal; and a first switch responsive to the controller and coupled between the output of the resistive touch pad and the first input of the controller; a second switch responsive to the controller and coupled between the output of the resistive touch pad and the second input of the controller; wherein the controller is operable to render the second switch conductive, such that the voltage at the second input is representative of whether the touch sensitive front surface is presently being actuated, and to render the first switch conductive such that the first capacitor is operable to stabilize the output voltage of the resistive touch pad and the voltage at the first input is representative of the position of the point actuation along the longitudinal axis.
 12. The user interface of claim 11, further comprising: a second capacitor coupled between the second input of the controller and the circuit common; and a first resistor coupled between the second input of the controller and the circuit common, such that the first resistor is coupled in parallel electrical connection with the second capacitor; wherein when the controller controls the second switch to be conductive, the parallel combination of the second capacitor and the first resistor is coupled between the longitudinal resistive element and the circuit common.
 13. The user interface of claim 12, wherein the controller renders the first and second switches conductive on a complementary basis.
 14. The user interface of claim 13, wherein the controller renders the first and second switches conductive on a periodic basis, such that the first switch is conductive for a substantially long period of time and the second switch is conductive for a substantially short period of time.
 15. The user interface of claim 14, wherein the second switch is rendered conductive for approximately 1% of the time.
 16. A method of reading outputs of a four-wire resistive touch pad having a longitudinal resistive element and a lateral resistive element for a load control device for controlling the amount of power delivered to an electrical load from an AC power source, the method comprising the steps of: coupling a DC supply voltage across the lateral resistive element; generating a first output voltage at the longitudinal resistive element in response to an actuation of the touch pad; determining that the actuation of the touch pad is presently occurring in response to the first output voltage; coupling the DC supply voltage across the longitudinal resistive element; generating a second output voltage at the lateral resistive element in response to the actuation of the touch pad; stabilizing the second output voltage; and controlling the amount of power provided to the electrical load in response to the second output voltage only when the first output voltage indicates that the touch pad is presently being actuated.
 17. The method of claim 16, further comprising the steps of: uncoupling the DC supply voltage from the lateral resistive element prior to the step of coupling in the DC supply voltage across the longitudinal resistive element; and uncoupling the DC supply voltage from the longitudinal resistive element prior to the step of coupling in the DC supply voltage across the lateral resistive element.
 18. The method of claim 16, wherein the step of stabilizing the second output voltage further comprises the step of: filtering the second output voltage to generate a filtered output voltage using a time constant ranging from approximately 6 milliseconds to 15 milliseconds.
 19. A load control device for controlling an amount of power delivered to an electrical load from an AC power source, the load control device comprising: a semiconductor switch operable to be coupled in series electrical connection between the source and the load, the semiconductor switch having a control input for controlling the semiconductor switch between a non-conductive state and a conductive state; a controller operatively coupled to the control input of the semiconductor switch for controlling the semiconductor switch between the non-conductive state and the conductive state; a touch sensitive front surface having a longitudinal axis and a lateral axis; a four-wire resistive touch pad responsive to a point actuation on the touch sensitive front surface, the resistive touch pad having a longitudinal resistive element for providing a first control signal representative of the position of the point actuation along the longitudinal axis to the controller, and a lateral resistive element for providing a second control signal representative of the position of the point actuation along the lateral axis to the controller; a first capacitor adapted to be coupled between the lateral resistive element and a circuit common, the first capacitor operable to charge and discharge through the longitudinal resistive element of the resistive touch pad to stabilize the first control signal; and first, second, and third switches responsive to the controller, each of the switches comprising first, second, and third terminals, and operable to be controlled between a first position in which the first terminal is electrically connected to the second terminal, and a second position in which the first terminal is electrically connected to the third terminal, the switches coupled to the four-wire resistive touch pad, such that when the controller controls all of the switches to the first position, a DC supply voltage is coupled across the longitudinal resistive element, the controller is coupled to the lateral resistive element, and the first capacitor is coupled between the lateral resistive element and the circuit common, and when the controller controls all of the switches to the second position, the DC supply voltage is coupled across the lateral resistive element and the controller is coupled to the longitudinal resistive element; wherein the controller is operable to determine if the touch sensitive front surface is presently being actuated in response to the second control signal, and to determine the position of the point actuation along the longitudinal axis in response to the first control signal.
 20. The load control device of claim 19, wherein the controller controls the switches between the first and second positions on a periodic basis, such that the switches are in the first position for a substantially long period of time and in the second position for a substantially short period of time.
 21. The load control device of claim 20, wherein the load control device is adapted to be coupled to an ac power source, and the controller controls the switches between the first and second positions on a periodic basis each half-cycle of the ac power source, such that the switches are in the second position for approximately 1% of each half-cycle. 